In a conventional electronic piano or other for playing in response to key depressions on the keyboard, an electronic sound source is controlled in accordance with the key stroke conditions, thereby generating sounds for playing. Such electronic piano is provided with a sensor below the key or at other positions for detecting the key stroke conditions. The sensor detects the touch information (touch data) including the key velocity (the key stroke strength). In addition, for modifying the sound generating level in accordance with the key stroke strength, the sensibility (the effectiveness) of the key touch is controlled for each key on the keyboard.
The effectiveness of the key touch defines the relationship between the key touch strength data and the output signal level (the sound level) which is transferred to the sound source. For example, as shown in FIG. 6, by applying an inclined line (touch curve) for modifying the data, a touch data before conversion (on the horizontal axis) is modified into a touch data after conversion (on the longitudinal axis). Based on the touch data after conversion, the output sound level is controlled.
For setting the effectiveness of the key touch, a map corresponding to the touch curve is stored in ROM or other in advance.
However, in a so-called piano with built-in electronic musical instrument, which is a combination of an acoustic piano and an electronic sound source so that it can be played using the electronic sound source in addition to usual piano playing, if a touch curve of conventional electronic piano is applied, the intensity of electronic sounds differ from that of natural piano sounds, which is a problem.
Since the keyboard of a piano with built-in electronic musical instrument is the same as that of an acoustic piano, the force transferred from the keyboard to the finger by an action system or other is of course largely different from that of a conventional electronic piano. Specifically, the action system of the piano has various characteristics for each key. Therefore, when it is played using the electronic sound source in the same manner as when played as an acoustic piano, the actual sounds generated from the electronic sound source (the electronic sounds) are significantly different from the sounds the player wishes to generate (the natural piano sounds). Further, the more the player gets used to the key touch of the acoustic piano, the more sense of incompatibility is felt in playing using the electronic sound source.